I purchased a 6.25” H4 headlight assembly from an E-bay seller for roughly $50. This was a round housing and headlight assembly with an H4 55/60W bulb included. All I found either had 6V or high wattage 12V bulbs. You need to order a 35/35W H4 bulb separately, available from many Ebay sellers. The original plan was to adapt the whole housing to my GTR since it mounted the same as the original, but would have to be drilled to mount the high beam and neutral lights. After disassembly, it looked as if the headlight itself could be mounted in the Bridgestone headlight rim using the clips included in the new assembly.

The photos below show the H4 headlight assembly purchased. There was a small notch at the bottom of the reflector. If yours comes apart like this, be certain to get the reflector and lens aligned properly when assembling.

It helps to know the flat on the H4 bulb base itself is the bottom of the bulb and, of course, get the lettering on the lens right side up.

Install male connectors on the ends of the H4 bulb leads or cut the ends off the BS headlight wires and splice to the ends of the H4 wires. I added connectors to the ends of the H4 wires and marked them with the Bridgestone harness colors using heat shrink tubing, but paint, labels or other methods could also be used.

I’d suggest ordering two 35/35W H4 bulbs so you have a spare. These aren’t going to be available at the local auto parts store if you need one quickly, although they may be available locally if you have a dealer that sells the small 50 or 125cc Chinese scooters. For the headlight assembly or lens assembly, search Ebay for a 6.24” H4 headlight. Many are listed for Honda CB750 or Yamaha XT500. Make certain it is a 6.25”. If you find a lens/bulb assembly without the housing, you can find the clips separately, but it may be cheaper to buy the whole assembly at once.

I measured the light output with my 50 year old light meter when checking the pattern in the first post above. It registered an approximate 70% increase in light output. When riding at night, it does make a significant difference.

I picked up my headlight the other day and pulled the rubber boot off and was surprised to see the replaceable bulb. Are the bulbs no longer available? I compared it to an H4 and it looks like with a little modification it would fit into the original lens and reflector. The filaments on the H4 don't stick into the housing as far as the original so it might not focus right. Has this been tried as I haven't seen any mention of it on this forum? Thanks Rod

That was my original intent - to install the H4 bulb into the original BS reflector. I modified the reflector so that the H4 tabs fit, but ran into the problem you quessed -the H4 will not go into the reflector far enough to provide the correct focus. The lip holding the rear piece (bulb alignment) to the main part of the reflector would have to be ground completely away, letting the pieces come apart. That's when I decided to try the whole headlight assembly.

I needed this so bad. I was trying to do this when my sealed beam went out on the 175. Same bulb. Failed at making a solid mounting point with my dremmel. Have you only found GTR lights or are there some for a 175 out there? I'll do some searching also just to see what's out there.

IIRC, the 175 has a 5 3/4" headlight, so do an Ebay search for "h4 5 3/4" headlight conversion". There seems to be plenty of choices of just the glass lens assembly with bulb. You'll have to buy the 35/35W H4 bulb separately unless you happen to find one that has that specific H4 bulb. You'll also need to buy the clips separately.

Resurrecting this old thread: I found that my 350 was having trouble keeping the battery charged; after an hour's ride or more, the battery would get low and I'd have trouble maintaining enough voltage to keep the bike running while sitting at a stop. After investigation, there were two problems: the alternator on my 350 is about .2 A low on output at 2900 RPM compared to a low mileage used one I have, and the H4 headlight bulb I installed draws approximately .5 A more on low and .3 A more on high than the stock bulb even though the H4 was rated at 35 Watts. Between the two, it was just too much. My solution was to convert to an LED taillight. It saves roughly .5 A current in taillight load and 1.6 A in brake light load. This has seemed to fix the problem; however, it is not as simple as switching bulbs due to the BS taillight design. I'll be posting photos from my conversion shortly in a separate thread.

It looks like it should work, so you won't be paying for a shell you don't need. You'll still need to buy a 35/35W bulb as that comes with a 55/60W. Good luck. It will be interesting to see if your 350 alternator will keep up without having to do the taillight bulb conversion too.

Just purchasing a lens/reflector unit won't get the clips like I used to mount it in the BS headlight shell, but those are the same as many small bikes used in the past and are probably available on Ebay. I think Hodakas and some Bridgestones used those, among others.

Search for Headlight lens clip, some old cars also used something similar.

Sounds like a great conversion, although I always thought the headlamp on the GTR was very good (compared to the 6v headlight on the HD sprint !!) and I am not familiar with the light levels available on current bikes. Was thinking maybe a lower wattage H4 bulb, say 25 or 30w if available, could be the answer to the power consumption issue while still providing a better light. I'm sure you would have considered this option, Karl.

At the time, I didn't find any H4s with less than the 35/35W rating. The LED conversion sounds like a good idea, should avoid any issues with lack of charging capacity. It should make a similar conversion on the 175/200's feasible also. I agree that the original 350 headlight wasn't too bad, but the 175 headlight leaves a lot to be desired. I'm sure the LED H4s are available here in the states also, so I'll check ebay. It will be interesting to see if the light pattern is still good. I use a 4' x 8' x 1/2'' sheet of styrofoam as a target to check the light pattern.

I modified the taillight to reduce the current requirements - see my post from Oct 27.

I used the replacement 1157 LEDs from Walmart, they look similar to those from most auto parts stores.

The one on the left is the original. Due to the construction of the Bridgestone taillight, the bulb won't fit into the socket far enough to engage. I ground off the OD of the circuit board nearest the socket to make it small enough to fit as shown in the right bulb.

The LED bulbs light the ring of LEDs nearest the socket for taillight, all of them for brake light. The 350 reflector is so shallow that the light goes to the side and none is reflected to the rear. I made a new deeper reflector to solve that problem using the cap off a cocktail shaker ($10 at Walmart). I installed a long screw through the top strainer, chucked it in the drill press, cut off the middle section, then pop riveted it to the taillight base.

The new reflector is shown below, starting with the cocktail shaker, bolt installed to chuck it in the drill press to use a cutoff wheel to remove the top and bottom and the finished reflector cut so it has tabs to pop rivet it to the existing reflector.. I tack welded the internal strainer before putting the bolt in to make certain it didn't come loose and I polished the inside to make it a better reflector.

There is surely a number of other household and workshop items that either have a reflector of the right size or could be modified to use, the cocktail shaker just caught my eye because it was stainless steel and a good shape.